The present invention relates to a wireless communication system in which a mobile station conducts wireless communication with a base station by using the simplex system. In particular, the present invention relates to a wireless communication system and a wireless communication method in which transmission right acquisition operation such as press button depressing operation (press operation) conducted by, for example, a user of a mobile station can be simplified.
For example, in a wireless communication system adopting the simplex system such as the press-to-talk system, the user depresses the press button when the mobile station is in the talkable state of the simplex system and operation for acquiring the transmission right (transmission right acquisition operation) is conducted. If the transmission right acquisition operation is conducted and message exchange with a higher rank apparatus can be conducted normally, the mobile station emits a sound for indicating the acquisition of the transmission right (transmission right acquisition sound) and passes into a state in which voice transmission is possible. On the other hand, when the message exchange with a higher rank apparatus cannot be conducted normally, or when acquisition of the transmission right is refused, the mobile station emits a sound for indicating a failure of the transmission right acquisition (transmission right acquisition failure sound) and passes into a state in which voice transmission is impossible. A base station or the like is used as the higher rank apparatus.
In the wireless system, the state of the air interface always changes due to the influence of whether the electric field is strong or weak, or whether the error rate is high or low, and the message exchange is not conducted normally in some cases. Furthermore, since the transmission right control is conducted in the higher rank apparatus, a refusal might be issued to a transmission right acquisition request from the mobile station for some reason.
A narrow band digital wireless communication system according to a FDMA (Frequency Division Multiple Access) system using the press-to-talk system is described in, for example, “Narrow Band Digital Telecommunication System (SCPC/FDMA),” ARIB STD-T61, published by Association of Radio Industries and Businesses, May 1999, pages 3, 5, 14, 16, 35, 36, 37 and 40.
With reference to FIGS. 7, 8 and 9, some typical conventional operation examples in wireless communication systems using the press-to-talk system will be described.
An example of press button operation in a mobile station and an example of a message exchange sequence between the mobile station and a base station which is a higher rank apparatus are shown in FIGS. 7, 8 and 9.
Specifically, a user of a mobile station No. 1 operates a press button, and the mobile station No. 1 acquires the transmission right via the base station which is a higher rank apparatus. Speech transmitted from the “mobile station No. 1” is transmitted to “another mobile station” via the “base station.” A flow of processing conducted in this case is shown.
In the case shown in FIG. 7, message exchange with the higher rank apparatus is not conducted normally in the “mobile station No. 1” for, for example, the reason that the mobile station is in a region insensitive to the radio wave. After nonestablishment of synchronous burst exchange has thus occurred once, the transmission right acquisition request is issued again and the transmission right is acquired.
In the case shown in FIG. 8, a refusal to permit transmission right acquisition is sent from the higher rank apparatus to the “mobile station No. 1” once by using a radio information channel (M=idle), and then the “mobile station No. 1” issues a transmission right acquisition request again and acquires the transmission right.
In the case shown in FIG. 9, a refusal to permit preservation of the transmission right is sent from the higher rank apparatus to the “mobile station No. 1” once by using a transmission cease request, and then the “mobile station No. 1” issues a transmission right acquisition request again and acquires the transmission right.
When the message exchange with the higher rank apparatus is not conducted normally, the transmission right acquisition is refused, or the “mobile station No. 1” is made to stop the transmission as shown in FIGS. 7, 8 and 9, the user temporarily releases the press button and depresses the press button again. As a result, subsequent processing is started.